The present invention relates to a solid-state imaging apparatus and a digital camera. More specifically, the present invention is directed to such a solid-state imaging apparatus and a digital camera, capable of acquiring an image having a reduced color fog, while a white balance when a photographic subject is photographed under plural sorts of light sources is corrected under better condition.
In digital cameras such as digital still cameras (containing digital still cameras mounted on portable telephones) and digital video cameras, photographic subjects are photographed by solid-state imaging elements such as CCDs and CMOS image sensors. Then, white balances of acquired image data as to the photographic subjects are corrected in response to sorts of illumination light sources for illuminating the photographic subjects, and then the corrected image data are outputted.
As light sources, various sorts of typically-known light sources have been predicted, e.g., the sunlight (D65 light source, D75 light source etc.), the normal type white color fluorescent light (F6 light source), and flash light. In the case that the digital cameras automatically perform the white balance correcting operations, the digital cameras analyze photographed image data so as to discriminate sorts of light sources from each other, and then use correction values in response to the discriminated sorts of light sources.
However, when a photographing operation is carried out, there are two cases. That is, in one case, a photographic subject is illuminated by employing only a single sort of light source; and in the other case, such a scene that a photographic subject is illuminated by employing plural sorts of light sources is photographed. For instance, there is such a case that an indoor scene is photographed under condition that the sunlight enters through a window into the interior area which is being illuminated by fluorescent light.
Conventionally, in the case that such an image data acquired by photographing a photographic subject is corrected by way of a white balance correcting operation while this photographic subject is illuminated by employing plural sorts of light sources, only one sort of such a light source which constitutes a main light source is judged, and then, an entire image is corrected based upon this judged sort of the light-source. As a result, the following problem occurs. That is, an image portion deviated from the main photographic subject within the image may cause color fogs, in other words, an image of such an image portion which is strongly illuminated by other sorts of light sources may cause the color fogs, so that this image may become, for example, a yellowish image. Therefore, the color reproducibility (especially, reproducibility of flesh color) is lowered.
To solve this problem, for example, the conventional technique described in the paragraph number [0026] of Japanese Laid-open Patent Application No. Hei-8-340542 (patent publication 1) has proposed the following technical ideas. That is, when the major photographic subject is photographed by actuating the electronic flash unit within the room which is being illuminated by the F6 light source, the influence amount of the flash light is calculated every image area of the photographed image based upon both the image data acquired from the solid-state imaging element before the flash light is emitted, and also, the image data acquired from the solid-state image element after the flash light is emitted. Then, the white balance correction amount with respect to each of the image areas is determined in response to this calculated influence amount, and thus, the image in which the white balance as to the entire image area has been controlled can be produced.
[Patent Publication 1]
Japanese Laid-open Patent Application No. Hei-8-340542 (paragraph number [0026])
However, the above-explained conventional technique of the patent publication 1 is directed only to the white balance in the case that the flash light is emitted, and requires such an arrangement that two sheets of such image data must be employed, namely, both the image data acquired before the flash light is emitted and the image data acquired after the flash light is emitted must be employed.
As a result, this conventional technique of the patent publication 1 cannot be applied to a white balance correcting operation in such a case that a photographic subject is photographed which is being illuminated by plural sorts of light sources other than flash light. This reason is given as follows: In the case that an indoor scene is photographed under such a condition that the sunlight is entered through a window of a room while the indoor area is being illuminated by fluorescent light, only one sheet of image data is acquired, but two sheets of such image data cannot be acquired. That is, both image data before the sunlight is illuminated, and image data after the sunlight is illuminated cannot be acquired.